In modern paint technology, automatic spraying techniques are often used for painting large articles or parts of articles, such as automobile bodies and electrical appliances such as refrigerators, in enclosed areas called paint spray booths. These booths have several purposes: (1) to contain any fumes or paint overspray, (2) to reduce the risk of contamination of the part being painted, and (3) to protect the health of the workers at the site. It is estimated that between about 20% to about 40% of the total volume of paint sprayed is overspray. In the application of organic paints such as epoxy resins, enamel paints and the like, it is necessary to trap the oversprayed paint. Smaller booths may employ filters to remove the paint overspray from the air, while larger systems usually use a recirculating water system for this purpose. In operation, the object to be painted generally passes through the work area of the booth. Air flow through the booth forces the paint overspray into intimate contact with the recirculating water, thereby effectively scrubbing the paint solids from the air into the water. This may be accomplished by forcing the air through any one of a water curtain, some type of water spray or a venturi scrubber, but the net effect of any of these processes is that oversprayed paint contacts and is captured by the recirculating water of the spray booth.
The amount of oversprayed paint contacting recirculating water in a paint spray booth may change depending on a number of variables, such as plant or process shutdowns, the size and shape of the object being painted, the type of spray equipment used, the spraying and purge techniques used, the type of paint used and the water flow rate. Even though improved coating methods have significantly reduced the amount of paint overspray, up to about 50% of the total paint sprayed may not reach the object being painted. As a result, significant concentrations of paint can build up in the system. Since the majority of paints used today must be baked at elevated temperatures in order to cure properly, the paint utilized can remain tacky indefinitely. The paint may coalesce into a mass of sticky material that can plug pipes, fans and recirculating pumps as well as build up on the walls of the paint spray booth itself, thus significantly reducing scrubbing efficiency in the booth and leading to an air imbalance which would not only result in a poor paint finish but also allow hazardous paint emissions to be discharged into the air. These conditions may also result in serious safety hazards to paint spray booth personnel. Federal regulations now limit the amount of volatile organic compounds (VOCS) that can be released at a given plant site, and organic solvent diluents used in solvent-based paint are a major source of VOCS. These VOCS are spontaneous combustion hazards.
Generally, the water collecting the paint overspray is recycled, and in order to ensure that the process continues to work efficiently, the paint must be collected and removed from the water. There is therefore a need to detackify the oversprayed paint so that it can be removed easily, thereby enabling filtration and recirculation of water through the system. Preferably, matting or coagulation of the oversprayed paint is also promoted so that the paint solids will either float so that they can be removed from the surface of the aqueous liquid in the spray booth, or the paint solids will sink so that they can be removed by sedimentation. However, efficient separation of the paint solids from the recirculating water to prevent clogging of the system can be expensive.
In addition, the resultant solid waste product collected by the filters of the wash booths are heavily contaminated with toxic materials and must be disposed of as hazardous waste. Disposal as hazardous waste requires the use of a hazardous materials disposal company, which can be very expensive.
The detackifying process (also known as paint denaturation or paint killing) takes place in the water phase by the addition of chemicals thereto. In addition, detackification is necessary because it prevents paint fouling the internal surfaces of the booth and of pipes, which may cause blockages. Collection of paint on the internal surfaces is undesirable because paint deposits formed on the internal walls of the booth are subject to the growth of anaerobic bacteria which generate corrosive and foul-smelling substances due to anaerobic decomposition of organic substances.
A variety of paint detackifier compositions have been described in the prior art, for example, in U.S. Pat. No. 6,136,200, issued to Waldmann on Oct. 24, 2000; U.S. Pat. No. 5,730,881, issued to Miknevich on Mar. 24, 1998; U.S. Pat. No. 5,298,186, issued to Mitchell et al on Mar. 29, 1994; U.S. Pat. No. 5,250,191, issued to Cory et al on Oct. 5, 1993; and U.S. Pat. No. 5,192,449, issued to Huang et al on Mar. 9, 1993, the contents of which are all expressly incorporated herein in their entirety by reference. However, the technology has not reached a fully satisfactory level, and the prior art detackifiers still result in the production of toxic solid waste and contaminated filters that must be disposed of as hazardous waste.
Therefore, there is a need in the art for improved compositions and methods for treatment of waste and filters from paint spray booths that overcome the cleanup, environmental and combustibility concerns of the prior art. It is to such improved compositions having detackification, detoxification and neutralization of combustibility properties and methods of using same in the treatment of waste and filters from paint spray booths that the present invention is directed.